Designing for Permanence - WoodWorks

Designing for Permanence: Protecting Wood Frame Structures from Insects and Decay Paul Coats, P.E., C.B.O.

Southeast Regional Manager American Wood Council

This presentation is protected by US and International Copyright laws. Reproduction,

distribution, display and use of the presentation without written permission of AWC is prohibited.

© American Wood Council 2016

Copyright

• The American Wood Council is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES), Provider # 50111237.

• Credit(s) earned on completion of this course will be reported to AIA CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request.

• This course is registered with AIA CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.

• Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

Description

When properly designed and constructed, wood-frame structures are able to resist damage by moisture and living organisms. This presentation focuses on four steps to achieving maximum service life with wood-frame structures: 1) controlling moisture content of wood, 2) providing effective termite controls, 3) using durable materials such as naturally durable or preservative-treated wood, and 4) instituting quality assurance. With an emphasis on best practice details and material specification, this session will present techniques for mitigating decay, insect infestation, and durability issues in new and existing wood construction.

Building Code Role

• State and local variations

• Code official is final authority

Graphic Source: www.awc.org

Conditions for Trees

• Moisture

• Air

Giant Sequoia 3000 years

Conditions for Organisms

Conditions necessary for wood-destroying organisms

• Moisture

• Oxygen

• Warm Temperature

• Food Source

Graphic Source: USDA FPL Wood Handbook

Stave Church – Norway – 1100 A.D.

Glacier Hotel – Montana – 1915

From Designing for Durability – reThinkWood.com

Photo courtesy of David Restivo, National Park Service; inset photo by T.J. Hileman, courtesy of Montana State University Library

Butler Brothers Building – Minneapolis - 1906


Building interior: Preservation Alliance of Minnesota; Building exterior: Butler Square

Proper Design for Maximum Service Life

• Control moisture content

• Termite barriers/details

• Naturally durable and preservative treated wood

• Quality assurance

Available free: www.awc.org

Best Practices - Construction

• Positive drainage

• Adequate separation

• Ventilation and condensation control

• Naturally durable and preservative treated wood

Moisture Content

• MC < 20%

• no decay

• MC > 25%

• optimum condition for decay

Graphic Source: Washington State University – Civil Engineering

• Liquid flow is most significant moisture load

• Rain

• Groundwater

Rain Exposure Zones

Graphic Source: WCD 6

Hygro-Thermal Zones

• Air movement and diffusion are less significant moisture contributors


Wood Equilibrium Moisture Content

Table Source: USDA Forest Products Lab Wood Handbook

Desorption

Resorption (adsorption) • More difficult • Prolonged exposure at high RH • Covered structures considered dry (<19%)

Moisture Control

• Site drainage

• Building drainage

• Separation of wood elements

• Condensation control

Material Handling and Storage

• EWP MC typically < 15%



Photo courtesy of KK Law

Weather Protection

• Close-in as quickly as possible

• Roof coverings

• Building envelope


Photo courtesy of Togawa Smith Martin, Inc.

Weather Protection

• Allow drying before installing insulation and gypsum

• Durability

• Shrinkage

• Structural Glulam – exposed (2015 IBC 2304.12.2.4)

• Solutions

• Preservative treated

• Naturally durable

• Under roof/eave

• Similar covering

• Top and end caps

• Industry practice

Detailing and Maintenance


• Structural Glulam – exposed – top/end cap details

Source: www.apawood.org


• Structural Glulam – exposed

• Tapered under roof

• Untreated


• Exposed poles & glulam

• Under roof overhang

• End caps


Photo courtesy of Brian Gassel, tvsdesign

Detailing and Maintenance - Ventilation

• Crawl space girder and floor joist

• 2015 IBC 2304.12.1.1

Detailing – Code Requirements


• Wood on concrete/masonry

• 2015 IBC 2304.12.1.2



• Siding

• 2015 IBC 2304.12.1.5





• Siding

• 2015 IRC R317.1 (5)

• 2015 IBC 2304.12.1.5

• Wood columns

• 2015 IBC 2304.12.2.2


Graphics Source: WCD 6



• Wood columns

• 2015 IBC 2304.12.2.2

Termite Damage

Termite Control

• Preservative treated wood

• Shields

• Chemical treatment

• Concrete foundations

• Concrete caps

• Inspection

Graphic Source: www.cwc.ca

Termite Control

• Not all “flying ants” are termites

Graphic Source: USDA Forest Products Lab Wood Handbook

Termite Control

Termite Shields


Termite Soil Treatment


Termite Control – Slab-on-Grade


• Essential to successful function of barrier and bait systems

Routine Maintenance/Inspection

Preservative Treatment

• Protects against insect attack and decay

Preservative Treatment

• Effectiveness

• Chemical type

• Penetration

• Retention

• Uniform distribution


Photo courtesy of BS&S Treated Lumber

Treatment Penetration

Graphic Source: USDA Forest Products Lab Wood Handbook

Refractory Species

Incising – Solid Sawn Lumber

• Design value adjustment per NDS for incising

• No adjustment for preservatives alone

• UC3B - Above Ground, Exposed

• Usually deck boards, rails, siding, joists, etc.

• UC4A - Ground Contact, General

• Soil, concrete, or fresh water contact items such as deck posts

• Some special heavy duty above ground applications like beams or girders

• UC4B - Ground Contact, Heavy

• For structural members difficult or expensive to replace

AWPA Standards

Source: www.awpa.com

AWPA Standards

Source: Western Wood Preservers Institute

Types of Preservatives

• Oil-borne or Oil-type

• Creosotes, pentachlorophenol

• Waterborne preservatives

• CCA, CA-B, ACQ, ACZA

• Non-pressure preservatives

• Water-repellents

Creosote - Marine

Creosote - Timber Bridge

Penta – Horse Stable

Penta – Timber Bridge

Penta – Utility Poles

Penta – Sound Barriers

Penta – Railroad Trestle

Waterborne - Permanent Wood Foundation

Source: Southern Forest Products Association

Waterborne - Decks

• Corrosion Resistance

• 2015 IRC R317.3

• 2015 IBC 2304.10.5

• Screws, bolts, nails

• Hot-dipped galvanized

• Stainless

• Silicon bronze

• Copper

• Hangers and anchors

• Galvanized

• Stainless

• Saltwater exposure

• Stainless

Waterborne - Fastener Corrosion

Grade Stamp

Field Treatment of Preservatives

• IBC silent

• IRC R317.1.1 and R318.1.2

• AWPA Standard M4 - Care of Preservative-Treated Wood Products

• Borates – interior

• Copper naphthenate or oxine copper – exterior

Naturally Durable Wood

• Decay resistant

• Redwood

• Cedars

• Black Locust

• Termite resistant

• Redwood

• Eastern Cedar

• Alaskan Yellow Cedar glulam and trusses

Los Angeles Reservoir Cover

Redwood Deck

Photo courtesy of California Redwood Association

Non-pressure Preservatives

• Water repellent preservatives

• Can be painted

• Oil-borne preservatives

• Not recommended for painting

• Dipping or vacuum process

• Moderate exposures

• Windows, siding, exterior trim, porch framing

Non-pressure Preservatives

• Water repellent preservatives

Table Source: USDA Forest Products Lab Wood Handbook

• Available from EPA and manufacturers

Safety Data Sheets

• Conformance to building codes

• Inspection by code officials

• Special inspection

• High wind and seismic detailing

• Conformance to standards

• Treated wood – quality mark

• AWPA standards

• Evaluation service reports

Quality Assurance

WCD 6 - Design for Permanence

• Decay / Termites

• Good Construction

• drainage

• separation

• condensation

• barriers

• Durability

• naturally

• pressure treated

• non-pressure treated Available free: www.awc.org

DCA 6 – Wood Deck Construction

• Good Practice

• Exposed to Elements

• Durability Issues

• Lumber

• Fasteners

Available free: www.awc.org

Other Resources

• USDA FPL Wood Handbook

Available free: www.fpl.fs.fed

Other Resources

• USDA FPL Moisture Management Series

Available free: www.fpl.fs.fed

Other Resources

• Canadian Wood Council – www.cwc.ca

Other Resources

• reThink WOOD – www.rethinkwood.com

Other Resources

• Woodworks – www.woodworks.org

Other Resources

• APA – www.apawood.org

• This concludes The American Institute of Architects Continuing Education Systems Course

Questions?

81

American Wood Council

[email protected]

www.awc.org

mailto:[email protected]

Designing for Permanence - WoodWorks

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